title: Synthesis of a tri- and a tetra-saccharide fragment of the capsular polysaccharide of type III group B Streptococcus.
abstract: Syntheses of the propyl glycosides (1-3) of beta-D-Galp-(1----4)-beta-D-GlcpNAc, beta-D-Glcp-(1----6)-[beta-D-Galp-(1----4)]-beta-D-GlcpNAc, and beta-D-Galp-(1----4)-beta-D-Glcp-(1----6)-[beta-D-Galp-(1----)]-beta-D- GlcpNAc, respectively, are reported. Reaction of allyl 2-acetamido-3-O-benzyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranos ide with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide under Hg(CN)2 catalysis, followed by oxidative removal of the 4-methoxybenzyl group, gave allyl 2-acetamido-3-O-benzyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-beta-D- galactopyranosyl)-beta-D-glucopyranoside (10) O-deacetylation of which, followed by hydrogenolysis/hydrogenation, gave 1. Reaction of 10 with beta-D-glucopyranose penta-acetate and beta-lactose octa-acetate, under catalysis by trimethylsilyl trifluoromethanesulfonate, and treatment of the products as for 10 gave 2 and 3, respectively. Attempted glycosylation of 10 with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl bromide under catalysis by Hg(CN)2 or silver trifluoromethanesulfonate gave an orthoester. Complete assignments of the 1H- and 13C-n.m.r. spectra of 1-3 are reported together with their carbon spin-lattice relaxation times which indicate that 3 assumes a compact instead of an extended shape.
authors.affiliation: National Research Council of Canada, Division of Biological Sciences, Ottawa, Ontario.
authors.forename: V
authors.initials: V
authors.lastname: Pozsgay
authors.forename: J R
authors.initials: JR
authors.lastname: Brisson
authors.forename: H J
authors.initials: HJ
authors.lastname: Jennings
mesh_terms: D002240:Carbohydrate Sequence; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D013292:Streptococcus agalactiae / Q000032:analysis; D014312:Trisaccharides / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; D014312:Trisaccharides; C032263:streptococcal polysaccharide type III group B